I've looked back to March this year using Google (to long ago for my news reader) for the last thread on foam guns.
As far as I can gather the strategy is that after use you take the foam can off, clean the top with cleaner, clean the outside of the gun, clean the inside with cleaner, then re-attach to the foam can.
This ties in with the instructions on the foam can and the cleaner can. There is, however, a Catch22 where you are supposed to have the part used foam attached to the gun and you may not know when you will next need it.
If you don't intend to use the gun again for an indeterminate time I assume you should leave it off the part used foam can and be prepared to throw the part used can away.
I am about to test this theory :-(
Our builders used my foam gun (I've never used it so far) and it looks nice and clean, and is attached to the can of foam.
However it must be about two years since it was used.
The foam still sounds liquid so I'll give it a go.
Is there any mileage in trying to run some cleaner through the gun before I try the foam?
I assume that if it is clear it will pass foam O.K. and if it is blocked then the cleaner will not be able to shift anything.
Oh, and which way should you twiddle the adjusting knob at the back? It is the Screwfix No Nonsense Foam Applicator Gun.
Cheers
Dave R